32 research outputs found
Na<sub>2</sub>Hg<sub>3</sub>M<sub>2</sub>S<sub>8</sub> (M = Si, Ge, and Sn): New Infrared Nonlinear Optical Materials with Strong Second Harmonic Generation Effects and High Laser-Damage Thresholds
A new family of noncentrosymmetric
isostructural compounds, Na<sub>2</sub>Hg<sub>3</sub>M<sub>2</sub>S<sub>8</sub> (M = Si, Ge, and
Sn), was successfully synthesized. They crystallize in the tetragonal
space group <i>P</i>4̅<i>c</i>2 with <i>Z</i> = 2. Their major structures are composed of infinite cross-connected <sub><i>∞</i></sub>(HgS<sub>3</sub>)<sub><i>n</i></sub> chains and isolated [MS<sub>4</sub>] ligands and show the
interesting tunnel features. Interestingly, compared with the structures
of A<sub>2</sub>Hg<sub>3</sub>M<sub>2</sub>S<sub>8</sub> (A = alkali
metal, Na–Cs), it can be found that the structural symmetries
show a gradually rising tendency from Cs to Na analogues as a result
of cation size effect, which rarely exists in quaternary alkali metal
chalcogenides. Property measurements show that title compounds exhibit
strong second harmonic generation (SHG) effects with a phase-matching
behavior at 2.09 μm, wide transparency range in the infrared
(IR) region, and large laser-damage thresholds (LDTs). Remarkably,
Na<sub>2</sub>Hg<sub>3</sub>Si<sub>2</sub>S<sub>8</sub> and Na<sub>2</sub>Hg<sub>3</sub>Ge<sub>2</sub>S<sub>8</sub> achieve the suitable
balance between large SHG effects (1.3 and 2.2 × benchmark AgGaS<sub>2</sub>) and high LDTs (4.5 and 3 × AgGaS<sub>2</sub>), respectively,
and can be expected to be potential nonlinear optical (NLO) candidates
in the IR region. Moreover, band structures and NLO properties of
title compounds are also theoretically studied, and the calculated
NLO coefficients are consistent with the experimental observations
Visible-Light-Mediated Construction of Pyrroloindolines via an Amidyl Radical Cyclization/Carbon Radical Addition Cascade: Rapid Synthesis of (±)-Flustramide B
The
development of visible-light-mediated synthesis of pyrroloindolines
via an amidyl radical cyclization–carbon radical functionalization
cascade is reported. The transformation shows a broad substrate scope,
tolerating a variety of substitutions on indole aromatic rings and
N-centers. Different functionalized alkene systems could be used as
radical acceptors. Relying on this strategy, a rapid synthesis of
flustramide B was achieved
Na<sub>2</sub>Hg<sub>3</sub>M<sub>2</sub>S<sub>8</sub> (M = Si, Ge, and Sn): New Infrared Nonlinear Optical Materials with Strong Second Harmonic Generation Effects and High Laser-Damage Thresholds
A new family of noncentrosymmetric
isostructural compounds, Na<sub>2</sub>Hg<sub>3</sub>M<sub>2</sub>S<sub>8</sub> (M = Si, Ge, and
Sn), was successfully synthesized. They crystallize in the tetragonal
space group <i>P</i>4̅<i>c</i>2 with <i>Z</i> = 2. Their major structures are composed of infinite cross-connected <sub><i>∞</i></sub>(HgS<sub>3</sub>)<sub><i>n</i></sub> chains and isolated [MS<sub>4</sub>] ligands and show the
interesting tunnel features. Interestingly, compared with the structures
of A<sub>2</sub>Hg<sub>3</sub>M<sub>2</sub>S<sub>8</sub> (A = alkali
metal, Na–Cs), it can be found that the structural symmetries
show a gradually rising tendency from Cs to Na analogues as a result
of cation size effect, which rarely exists in quaternary alkali metal
chalcogenides. Property measurements show that title compounds exhibit
strong second harmonic generation (SHG) effects with a phase-matching
behavior at 2.09 μm, wide transparency range in the infrared
(IR) region, and large laser-damage thresholds (LDTs). Remarkably,
Na<sub>2</sub>Hg<sub>3</sub>Si<sub>2</sub>S<sub>8</sub> and Na<sub>2</sub>Hg<sub>3</sub>Ge<sub>2</sub>S<sub>8</sub> achieve the suitable
balance between large SHG effects (1.3 and 2.2 × benchmark AgGaS<sub>2</sub>) and high LDTs (4.5 and 3 × AgGaS<sub>2</sub>), respectively,
and can be expected to be potential nonlinear optical (NLO) candidates
in the IR region. Moreover, band structures and NLO properties of
title compounds are also theoretically studied, and the calculated
NLO coefficients are consistent with the experimental observations
Na<sub>4</sub>MgM<sub>2</sub>Se<sub>6</sub> (M = Si, Ge): The First Noncentrosymmetric Compounds with Special Ethane-like [M<sub>2</sub>Se<sub>6</sub>]<sup>6–</sup> Units Exhibiting Large Laser-Damage Thresholds
Two
new noncentrosymmetric compounds, Na<sub>4</sub>MgM<sub>2</sub>Se<sub>6</sub> (<b>I</b>, M = Si; <b>II</b>, M = Ge), that contain
special ethane-like [M<sub>2</sub>Se<sub>6</sub>]<sup>6–</sup> units were reported for the first time. Remarkably, they exhibit
high laser-damage thresholds [9 (<b>I</b>) and 7 (<b>II</b>) × benchmark AgGaS<sub>2</sub>] and moderate second-harmonic-generation
responses with type I phase matching
Synthesis and Characterization of Mid-Infrared Transparency Compounds: Acentric BaHgS<sub>2</sub> and Centric Ba<sub>8</sub>Hg<sub>4</sub>S<sub>5</sub>Se<sub>7</sub>
Two
mid-IR transparency compounds, namely, acentric BaHgS<sub>2</sub> (BHS)
and centric Ba<sub>8</sub>Hg<sub>4</sub>S<sub>5</sub>Se<sub>7</sub> (BHSSe), were successfully synthesized by a conventional
solid-state reaction method. The space group of BHS is orthorhombic <i>Pmc</i>2<sub>1</sub> with [HgS<sub>4</sub>] tetrahedra and isolated
dumbbell-shaped [HgS<sub>2</sub>] units, while BHSSe belongs to the
orthorhombic space group <i>Pnma</i> with infinite isolated <sub>∞</sub>[HgSe<sub>2</sub>(S/Se)<sub>2</sub>]<sup>4–</sup> chains. Raman spectra and thermal analysis of the titled materials
were measured. In addition, their band gaps are found to be 1.93 (BHS)
and 1.98 eV (BHSSe) from the measured diffuse reflectance spectra.
Significantly, the powder BHS sample exhibits a good second harmonic
generation (SHG) response of ∼6.5 times compared with that
of reference AgGaS<sub>2</sub> at a fundamental wavelength (2.09 μm).
The calculated SHG coefficients of BHS are also reported, and the
maximum result agrees well with the test observation
Synthesis and Characterization of Mid-Infrared Transparency Compounds: Acentric BaHgS<sub>2</sub> and Centric Ba<sub>8</sub>Hg<sub>4</sub>S<sub>5</sub>Se<sub>7</sub>
Two
mid-IR transparency compounds, namely, acentric BaHgS<sub>2</sub> (BHS)
and centric Ba<sub>8</sub>Hg<sub>4</sub>S<sub>5</sub>Se<sub>7</sub> (BHSSe), were successfully synthesized by a conventional
solid-state reaction method. The space group of BHS is orthorhombic <i>Pmc</i>2<sub>1</sub> with [HgS<sub>4</sub>] tetrahedra and isolated
dumbbell-shaped [HgS<sub>2</sub>] units, while BHSSe belongs to the
orthorhombic space group <i>Pnma</i> with infinite isolated <sub>∞</sub>[HgSe<sub>2</sub>(S/Se)<sub>2</sub>]<sup>4–</sup> chains. Raman spectra and thermal analysis of the titled materials
were measured. In addition, their band gaps are found to be 1.93 (BHS)
and 1.98 eV (BHSSe) from the measured diffuse reflectance spectra.
Significantly, the powder BHS sample exhibits a good second harmonic
generation (SHG) response of ∼6.5 times compared with that
of reference AgGaS<sub>2</sub> at a fundamental wavelength (2.09 μm).
The calculated SHG coefficients of BHS are also reported, and the
maximum result agrees well with the test observation
New Compressed Chalcopyrite-like Li<sub>2</sub>BaM<sup>IV</sup>Q<sub>4</sub> (M<sup>IV</sup> = Ge, Sn; Q = S, Se): Promising Infrared Nonlinear Optical Materials
Chalcopyrite-type
AgGaQ<sub>2</sub> (Q = S, Se) and ZnGeP<sub>2</sub> are the main commercial
infrared nonlinear optical (IR NLO) crystals.
Unfortunately, performance defects including low laser damage threshold
(LDT), harmful two-photon absorption (TPA), or small birefringence
limit their application. With this background, four new compressed
chalcopyrite-like IR NLO materials Li<sub>2</sub>BaM<sup>IV</sup>Q<sub>4</sub> (M<sup>IV</sup> = Ge, Sn; Q = S, Se) were successfully synthesized
with the typical AgGaQ<sub>2</sub> as templates. Remarkably, Li<sub>2</sub>BaGeS<sub>4</sub> and Li<sub>2</sub>BaSnS<sub>4</sub> not
only maintain the good NLO responses (0.5 and 0.7 × AgGaS<sub>2</sub>) but also overcome low LDTs and TPA of commercial chalcopyrites,
demonstrating that they satisfy critical demands as promising IR NLO
candidates. All of them exhibit phase-matching abilities. Furthermore,
the discovery of chalcopyrite-like compounds also provides a feasible
design strategy to explore new promising IR NLO materials
Rh(III)-Catalyzed Intermolecular C–H Amination of 1‑Aryl‑1<i>H</i>‑pyrazol-5(4<i>H</i>)‑ones with Alkylamines
An
intermolecular C–H amination of 1-aryl-1<i>H</i>-pyrazol-5Â(4<i>H</i>)-ones was achieved under mild reaction
conditions, using a low catalyst loading and with a broad scope of
aminating reagents. This protocol not only provides the first example
of rhodiumÂ(III)-catalyzed intermolecular aromatic C–H amination
directed by an intrinsic functionality of the substrate/product but
also features aminating an existing drug with either primary or secondary <i>N</i>-benzoate alkylamines as the coupling partners
Rh(III)-Catalyzed Intermolecular C–H Amination of 1‑Aryl‑1<i>H</i>‑pyrazol-5(4<i>H</i>)‑ones with Alkylamines
An
intermolecular C–H amination of 1-aryl-1<i>H</i>-pyrazol-5Â(4<i>H</i>)-ones was achieved under mild reaction
conditions, using a low catalyst loading and with a broad scope of
aminating reagents. This protocol not only provides the first example
of rhodiumÂ(III)-catalyzed intermolecular aromatic C–H amination
directed by an intrinsic functionality of the substrate/product but
also features aminating an existing drug with either primary or secondary <i>N</i>-benzoate alkylamines as the coupling partners
Na<sub>2</sub>ZnGe<sub>2</sub>S<sub>6</sub>: A New Infrared Nonlinear Optical Material with Good Balance between Large Second-Harmonic Generation Response and High Laser Damage Threshold
The development of frequency-conversion
technology in the infrared
region is in urgent need of new excellent infrared nonlinear optical
(IR NLO) materials. How to achieve a good balance between laser damage
threshold (LDT) and NLO coefficient (<i>d</i><sub><i>ij</i></sub>) for new IR NLO candidates is still a challenge.
The combination of the highly electropositive alkali metal (Na) and
Zn with <i>d</i><sup>10</sup> electronic configuration into
crystal structure affords one new IR NLO material, Na<sub>2</sub>ZnGe<sub>2</sub>S<sub>6</sub>. It exhibits excellent properties including
a wide transparent region (0.38–22 μm), large band gap
(3.25 eV), and especially a balance between a strong NLO coefficient
(30-fold that of KDP) and a high LDT (6-fold that of AgGaS<sub>2</sub>), indicating a promising application in the IR region. Moreover,
novel common-vertex-linked wavelike <sub>∞</sub>[GeS<sub>3</sub>]<sub><i>n</i></sub> chains are interestingly discovered
in Na<sub>2</sub>ZnGe<sub>2</sub>S<sub>6</sub>, which rarely exist
in the reported thiogermanides containing alkali metals. In addition,
calculated SHG density and dipole moment demonstrate that the large
NLO response is mainly attributed to the cooperative effects of the
[GeS<sub>4</sub>] and [ZnS<sub>4</sub>] units